We have developed an electro-acupuncture device which has proven effective for the control of nausea and vomiting. The device, marketed under the trademark Relief-Band®, is worn on the wrist like a wristwatch, with a watch-like housing which is positioned on the underside of the wrist. The device is described in Bertolucci, Nausea Control Device, U.S. Pat. No. 4,981,146 (Jan. 1, 1991), and in our co-pending application Electro-Acupuncture Device with Stimulation Electrode Assembly, filed Nov. 22, 2000, and incorporated herein in its entirety. The housing has two electrodes on the inside face (the face in contact with the wrist when secured to the wrist), a battery and circuitry inside the housing, and control buttons on the outer face. A patient suffering from nausea or vomiting (from motion sickness, morning sickness, chemotherapy, or anesthesia) can strap the device onto their wrist and turn it on. When turned on, the device emits an electrical stimulation pulse over the P6 acupuncture point (corresponding to the superficial course of the meridian nerve through the wrist). Within several minutes, most patients experience a substantial relief of nausea. The device uses non-invasive nerve stimulation whereby electricity is passed through two electrodes to stimulate nerves located on the ventral side of the wrist (this anatomical position is sometimes referred to as the palmar side of the wrist). The treatment provided by the device is sometimes referred to as electro-acupuncture, which is a form of acupuncture, and the ventral site of application is referred to in the acupuncture art as the P6 point, pericardium 6 point, or master point of the pericardium meridian (sometimes referred to as the vascular meridian). A primary object of the invention is to provide a non-chemical, non-invasive, painless and inexpensive method of alleviating nausea. The device is also portable, self-contained and convenient to the patient. Electrical pulse repetition rate of approximately 70 pulses per second and a pulse width of 80 microseconds has been found to provide effective relief of nausea in a patient. Our currently preferred electrical pulse pattern comprises about 350 microsecond pulse width at about 31 pulses per second at power levels of about 10–35 milli-amps peak pulse height. Thus a wide range of pulse patterns may be used in non-invasive nerve stimulation devices.
The stimulation and effect of our electro-acupuncture products are greatly enhanced if a conductive gel is used in conjunction with the electro-acupuncture device. This gel serves as an electronic to ionic current conversion layer (or an impedance matching layer) between the electrodes and the dry outer skin layer. This electrical conduction layer, sometimes referred to as an impedance matching layer, greatly enhances the effect of the device and lowers the power requirements for the device. The patient applies the gel to the skin before strapping the device onto the wrist. The gel may be referred to as a conductivity gel or an electro-medical coupling agent.
Hydrogel is a common component used in medical electrode devices. Riazzi et al., Biomedical Electrode Having A Secured One-Piece Conductive Terminal, U.S. Pat. No. 5,511,548, discloses an assembly comprising a conductive hydrogel layer having two surfaces, one surface adapted to adhesively contact the skin, a porous scrim applied to the other surface of the hydrogel layer for support of the hydrogel layer, and an electrode integrally attached to the scrim and in contact with the hydrogel layer through the pores of the scrim. The assembly provides for electrical conduction from the one electrode, through the pores to the hydrogel layer, and to the skin. Stratbucker, Electrocardiograph Bioelectric Interface System and Method of Use, U.S. Pat. No. 5,938,597 discloses a pair of EKG electrodes covered by a single sheet of hydro-polymer. A slit is present in the hydro-polymer sheet and in between two electrodes. The slit prevents transmission of EKG signals at one electrode to the other electrode through the gel layer.
A limitation on the use of a conductive hydrogel with our electro-acupuncture device is that it is possible for some users to apply too little of the gel and thus reduce the effectiveness of the device. Additionally, applying too much hydrogel can cause the electrodes to short, thereby reducing the effectiveness of the device. The gel can also be washed away or rubbed off during use. Some users find the gel too messy and inconvenient to deal with. As a result, the user may abandon the device in favor of the drugs intended to be replaced by the device. As an alternative to the gel, we have developed a hydrogel coating which adheres to the electrodes and can be applied to the electrodes during manufacture or by the user. The provision of the hydrogel during manufacture enhances effectiveness of the device since it eliminates the possibility that some users will apply too much gel or too little gel. The provision of the hydrogel pad in user-replaceable form also enhances effectiveness eliminating the possibility that some users will apply too much gel or too little gel.